The overall objective of this proposal is to characterize the immune system of the human male genital tract and to explore immunization routes and forms of antigens that are effective in the induction of humoral and cellular immune responses. Because systemic immunizations is usually ineffective at inducing specific immune responses in mucosal tissues and secretions, novel strategies have to be developed to generate protective responses to HIV at the most frequent site of entry. The purpose of the proposed studies is to determine the origin and properties of antibodies in male genital tract secretions, determine whether the mucosal component of the male genital tract belongs to the common mucosal immune system, and evaluate the efficacy of various mucosal and systemic immunization routes and antigen delivery systems that induce humoral and cellular immune responses in the human male genital tract. To achieve these goals, molecular properties of mucosal antibodies in the male genital tract secretions (pre-ejaculate and semen) will be characterize with respect to the antibodies in the male genital tract secretions (pre-ejaculate and semen) will be characterized with respect to the isotype, characteristics of IgA (proportions of monomeric, polymeric, and secretory IgA), the specificity of naturally occurring antibodies to environmental microbial and food antigens (as compared to other external secretions and serum), and properties and specificity of antibodies and cytotoxic T lymphocytes induced by mucosal (nasal, oral, and rectal) and systemic routes of immunization with microbial vaccines. In the selection of suitable antigens for human administration, live and inactivated commercially available poliovirus and influenza virus vaccines and live Salmonella typhi Ty21A vaccine were considered as prototype antigens and vectors that are relevant to the vaccine delivery systems for HIV antigens. In addition, recombinant cholera toxin B subunit, a potent mucosal antigen and adjuvant, will be used for oral and possibly intranasal immunization (and combination of routes) and the ensuing humoral and cellular responses in peripheral blood and external secretions will be evaluated. The properties of antibodies induced in the systemic and mucosal compartments will be determined with respect to the isotype, magnitude, and duration after different routes of administration of live and inactivated vaccines. The accumulated information will provide a rational basis for effective and practical immunization protocols that are effective in generation of immune responses against genitally acquired HIV infection.